Organic light emitting display

• US 7,411,571 B2
• Filed: 04/29/2005
• Issued: 08/12/2008
• Est. Priority Date: 08/13/2004
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: Huh, Jin
• Primary Examiner(s): Dinh; Trinh Vo
• Assistant Examiner(s): DUONG, DIEU HIEN
• Application Number:
  US11/117,466
• Publication Number:
  US 20060033449A1
• Time in Patent Office: 1,201 Days
• Field of Search: 315/169.2, 315/169.3, 315/196.2, 345/55, 345/76, 345/77, 345/80, 345/84, 345/82
• US Class Current: 345/80
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An organic light emitting display that is capable of preventing degradation of picture quality, and a method of manufacturing the organic light emitting display are provided. A unit pixel for the organic light emitting display, includes a first transistor coupled to a data line and having a first voltage threshold, a second transistor coupled to the first and third transistors and controlled by a second select signal, a third transistor coupled to the first transistor and controlled by a first select signal, and a fourth transistor coupled to the third transistor and having a fourth voltage threshold such that a drive current of the fourth transistor is controlled independent of the fourth voltage threshold.

Claims

1. A unit pixel for an organic light emitting display, the unit pixel comprising:

first to fourth transistors;

a capacitor coupled to one of the first to fourth transistors,

wherein two of the first to fourth transistors function as switching devices, one of the first to fourth transistors functions as a driving device, and one of the first to fourth transistors functions as a diode device, and

wherein the one transistor functioning as the diode device is connected directly to a data line, but not directly to a scan line;

an organic light emitting diode (OLED); and

a fifth transistor connected between the fourth transistor and the OLED to prevent a current from the fourth transistor from flowing to the OLED during an initialization.

2. A unit pixel for an organic light emitting display, the unit pixel comprising:

a first transistor coupled to a data line and having a first voltage threshold;

a second transistor coupled to the first transistor and a third transistor and controlled by a second select signal;

the third transistor coupled to the first transistor and controlled by a first select signal;

a fourth transistor coupled to the third transistor and having a fourth voltage threshold,

wherein a drive current of the fourth transistor is controlled independent of the fourth voltage threshold, and

wherein the first transistor functions as a diode device and is connected directly to a data line;

an organic light emitting diode (OLED); and

a fifth transistor connected between the fourth transistor and the OLED to prevent a current from the fourth transistor from flowing to the OLED during an initialization.

3. The unit pixel of claim 2, wherein the first voltage threshold is equal to the fourth voltage threshold.

4. The unit pixel of claim 2, further comprising:

first and second select signal lines respectively supplying the first and second select signals.

5. The unit pixel of claim 2, further comprising:

an initialization voltage line supplying an initialization voltage to the second transistor.

6. The unit pixel of claim 2, wherein the fifth transistor is controlled by a third select signal.

7. The unit pixel of claim 2, wherein a voltage from the OLED functions as an initialization voltage for the second transistor.

8. The unit pixel of claim 2, wherein the second select signal functions as an initialization voltage for the second transistor.

9. The unit pixel of claim 2, wherein the first select signal controls both the third and fifth transistors.

10. The unit pixel of claim 9, wherein the second select signal functions as an initialization voltage for the second transistor.

11. The unit pixel of claim 9, wherein a voltage from the OLED functions as an initialization voltage for the second transistor.

12. The unit pixel of claim 2, wherein the first through fifth transistors are of the same type.

13. The unit pixel of claim 2, wherein the third and fifth transistors are opposite type transistors.

14. The unit pixel of claim 2, wherein at least the second and the fifth transistors are of a type that is opposite to a type of the first, third or fourth transistor.

15. The unit pixel of claim 2, further comprising:

a capacitor coupled between the third transistor and a power voltage source.

16. An organic light emitting display device comprising:

a plurality of unit pixels, each unit pixel including,

a first transistor coupled to a data line and having a first voltage threshold,

a second transistor coupled to the first transistor and a third transistor and controlled by a second select signal,

the third transistor coupled to the first transistor and controlled by a first select signal,

a fourth transistor coupled to the third transistor and having a fourth voltage threshold,

wherein a drive current of the fourth transistor is controlled independent of the fourth voltage threshold, and

wherein the first transistor functions as a diode device and is connected directly to a data line, an organic light emitting diode (OLED), and a fifth transistor connected between the fourth transistor and the OLED to prevent a current from the fourth transistor from flowing to the OLED during an initialization.

17. The display device of claim 16, wherein for the each unit pixel, the first voltage threshold is equal to the fourth voltage threshold.

18. The display device of claim 16, wherein for the each unit pixel, the fifth transistor is controlled by a third select signal.

19. The display device of claim 16, wherein for the each unit pixel, a voltage from the OLED functions as an initialization voltage for the second transistor.

20. The display device of claim 16, wherein for the each unit pixel, the second select signal functions as an initialization voltage for the second transistor.

21. The display device of claim 16, wherein for the each unit pixel, the first select signal controls both the third and fifth transistors.

22. The display device of claim 21, wherein for the each unit pixel, the second select signal functions as an initialization voltage for the second transistor.

23. The display device of claim 21, wherein for the each unit pixel, a voltage from the OLED functions as an initialization voltage for the second transistor.

24. A display device comprising:

a first transistor connected to a first node to initialize the first node in response to a first select signal, the first transistor having a first threshold voltage;

a second transistor connected between the first node and a second node to initialize the second node in response to a second select signal;

a third transistor connected to the first node to supply a data voltage to the second node, the data voltage being dropped as much as the first threshold voltage;

a fourth transistor connected to the second node to supply a driving current to an organic light emitting diode (OLED), the fourth transistor having a second threshold voltage to offset the first threshold voltage,

wherein the first threshold voltage of the first transistor is identical to the second threshold voltage of the fourth transistor, and

the first transistor functions as a diode device and is connected directly to a data line; and

a fifth transistor connected between the fourth transistor and the OLED to prevent a current from the fourth transistor from flowing to the OLED during an initialization operation.

25. The display device of claim 24, wherein the

fifth transistor connected between the fourth transistor and the OLED blocks the current supplied from the fourth transistor to the OLED during an initialization operation in response to the first select signal.

26. A unit pixel for an organic light emitting display, the unit pixel comprising:

a first component coupled to a data line;

first and second select signal lines to supply respectively first and second select signals;

a second component coupled to the first component and controlled by the second select signal;

a third component coupled to the first component and controlled by the first select signal;

a fourth component coupled to the third component and supplying a driving current to an organic light emitting diode (OLED),

wherein the first component is connected directly to the data line, but not directly to any of the first and second select signal lines; and

a fifth component connected between the fourth component and the OLED to prevent a current from the fourth component from flowing to the OLED during an initialization operation.

27. The unit pixel of claim 26, wherein the first, second, third and fourth components are transistors.

28. The unit pixel of claim 26, wherein the

fifth component is controlled by either the first select signal or a third select signal and prevents a current flow to the OLED during an initialization of the third component.

29. A method of manufacturing an organic light emitting display device, the method comprising:

forming an organic light emitting display panel including a plurality of unit pixels, each unit pixel including,

a first transistor coupled to a data line and having a first voltage threshold,

a second transistor coupled to the first transistor and a third transistors and controlled by a second select signal,

the third transistor coupled to the first transistor and controlled by a first select signal,

a fourth transistor coupled to the third transistor and having a fourth voltage threshold such that a drive current of the fourth transistor is controlled independent of the fourth voltage threshold, wherein the first transistor functions as a diode device and is connected directly to a data line, an organic light emitting diode (OLED), and a fifth transistor connected between the fourth transistor and the OLED to prevent a current from the fourth transistor from flowing to the OLED during an initialization operation.

30. The method of claim 29, wherein the first voltage threshold is equal to the fourth voltage threshold.

31. The method of claim 29, further comprising:

forming first and second select signal lines for each of the unit pixels to respectively supply the first and second select signals.

32. The method of claim 29, further comprising:

forming an initialization voltage line to supply an initialization voltage to the second transistor in each of the unit pixels.

33. The method of claim 29, wherein for each of the unit pixels, the fifth transistor is controlled by a third select signal.

34. The method of claim 29, wherein for each of the unit pixels, a voltage from the OLED functions as an initialization voltage for the second transistor.

35. The method of claim 29, wherein for each of the unit pixels, the second select signal functions as an initialization voltage for the second transistor.

36. The method of claim 29, wherein for each of the unit pixels, the first select signal controls both the third and fifth transistors.

37. The method of claim 36, wherein for each of the unit pixels, the second select signal functions as an initialization voltage for the second transistor.

38. The method of claim 36, wherein for each of the unit pixels, a voltage from the OLED functions as an initialization voltage for the second transistor.

39. The method of claim 29, wherein for each of the unit pixels, the first through fifth transistors are of the same type.

40. The method of claim 29, wherein for each of the unit pixels, the third and fifth transistors are opposite type transistors.

41. The method of claim 29, wherein for each of the unit pixels, at least the second and the fifth transistors are of a type that is opposite to a type of the first, third or fourth transistor.

42. The method of claim 29, further comprising:

forming, in each of the unit pixels, a capacitor coupled between the third transistor and a power voltage source.